FIGS. 1 and 2 show a scroll compressor as one example of a scroll fluid machine, including an orbiting scroll.
An orbiting end plate 3 of an orbiting scroll 1 has a plurality of cooling fins 2 on the inner surface, and an orbiting wrap 4 on the outer surface. A plurality of extensions 5, such as two or three, is provided on the outer circumference of the orbiting end plate 3.
At the end of the extension 5, there is provided a boss 7 having an axial hole 6 perpendicular to the surface of the orbiting end plate 3. A crank-pin type self-rotation-preventing eccentric shaft 8,8a engages in the axial hole 6 via a ball-bearing 9.
The lower self-rotation-preventing eccentric shaft 8a is driven by a suitable power.
The orbiting scroll 1 comprises two halves fastened to each other, but does not relate to the present invention. Its illustration and description are omitted.
The front and rear surfaces of the orbiting scroll 1 engage on stationary scrolls 13, 13 each having a stationary wrap 12 on a stationary end plate 11. The orbiting wrap 4 engages with the stationary wrap 12 to form crescent sealed chambers.
The each end of the self-rotation-preventing eccentric shaft 8 projecting from the boss 7 is pivotally connected to bearings 14, 15 of the stationary end plate 11.
By rotating the lower self-rotation-preventing eccentric shaft 8a by a power, the orbiting scroll 1 is eccentrically revolved between the two stationary scrolls 13 and 13, so that volume in the sealed chamber gradually reduces toward the center or gradually increases radially outward to allow fluid sucked on the outer circumference to be compressed toward the center or to allow fluid sucked at the center to be decompressed and discharged from the outer circumference.
However, depending on changes in surrounding temperature and conditions of use, it is difficult to keep exact positional relationship of the three self-rotation-preventing eccentric shafts 8,8a and distance or inclination between them and the center of the orbiting scroll 1 as originally designed.
In many cases, they are caused by local wear of the bearing for the self-rotation-preventing eccentric shaft not to result in uniformity in load and side pressure to the boss of the self-rotation-preventing eccentric shaft to develop local wear and local load. Thus, performance and durability decrease and noise occurs.